This invention relates to a method for producing a cement for medical use according to which a liquid component containing a polymerizable substance is combined with a solid component comprising a plastic substance to provide a setting mass to form the cement. The polymerizable substance of the liquid component is generally monomer methacrylate and the plastic substance of the solid component is generally polymer methacrylate. In the present invention, a crystalline ceramic material is mixed with the plastic substance before combining the solid and liquid components.
The invention also relates to a cement for such uses and to the use of set cement as an anchorage for the fixation of prostheses or parts of prostheses or bone and as a substitute material for bone.
The use of anchorage substances in surgical procedures, especially for implants, has led to the development of so-called bone cement. The most common use of bone cement has been to fill the gap between a joint implant and tissue, primarily bone. As the cement sets around an implant immediate fixation will be achieved. When bone cement is used, weight bearing is generally allowed within the first postoperative days. The most important complication hitherto has been infection, joint implants breakage or dislocation. Through strict aseptic and antiseptic measures and methodologic development, the most severe problems today are wear of the polymer component and loosening between the metallic and polymer implants and bone leading to an interface failure with bone resorption and loss of implant anchorage. An improvement of material and technique has been going on since joint implant procedure with the bone cement started in the late 1950's through cooperation between researchers, engineers, manufacturers and surgeons.
The most important development in the area of bone cement has been a change of the additives used in bone cement. Various substances with particles between 20-300 micrometers in size have been used. Particulate additive powder has mainly been used in a spherical form. This may be regarded as the accepted technique today. Both resorbable particulate powder such as tri-calcium phosphate and non resorbable powder such as zirconium oxide have been used. The addition of particulate powder varies between about 5% to about 30% with about 20% to about 25% being the preferred amount. In contrast to the additives which have a secondary role, for example zirconium oxide or barium sulphate which produce a radiopaque bone cement, and tri-calcium phosphate which produces a porous cement, new additives will have to be developed to improve both the biological and mechanical properties of bone cement.